How to Make Walnuts Release Their Oil

Walnut oil is an ingredient in salad dressing -- and paint.

Walnut oil is an expensive specialty oil that is light in color and nutty in flavor. It is used primarily in salad dressings, sauces and gourmet recipes, but it is not a cooking oil, as it burns easily and loses its flavor at high temperatures. Walnut oil can also be used to make soaps; hair and body oils; and paints. The intensity of the nutty flavor of walnut oil can be easily affected by minor variations in its production, and it may take some time and experimentation to produce an oil with the particular flavor you desire.

Things You'll Need

• Walnuts
• Nutcracker
• Bowl
• Chopping Knife
• Cutting Board
• Baking Tray
• Oven
• Oil press
• Sealable glass or plastic container

Instructions

Prepare the Walnuts

1. Crack the shells of the walnuts. Remove the shells and the husks, and sort the nuts into a bowl.

2. Clean the nuts by brushing off any dust or particles.

3. On a cutting board, chop the nuts into small pieces.

4. Spread the nuts evenly on a baking tray.

Roast the Walnuts

1. Preheat the oven to 350 degrees F.

2. Place the tray of walnuts in the center of the oven.

3. Bake for 5 -10 minutes, stirring frequently, until the nuts are lightly browned. If any of the light husks were still on the nuts after cleaning, they will begin to peel off. This is a sign that you should remove the nuts from the oven.

Press the Walnuts

1. Place the nuts in the cage or cylinder of the oil press. The volume of nuts you can process at one time will depend on the size of your oil press.

2. Depending on the type of oil press you have, either turn the hand crank or switch on the appliance, and the press will crush the nuts.

3. Collect the walnut oil as it drips from the machine.

4. Pour the oil into a clean, dry container and seal tightly. Store the oil in a cool, dry place.

Tips & Warnings

• Roasting is necessary to produce a rich, nutty flavor in walnut oil. There is a large degree of flexibility in roasting walnuts, as the temperature and roasting time will affect the nuances of the flavor of the oil. Walnuts can be roasted at oven temperatures from 100 to 375 degrees F, but they burn quickly. However you choose to roast them, keep a close eye on them. Under-roasting will not release much nutty flavor, but over-roasting can add a burnt flavor. The length of time you roast the walnuts will depend on what flavor you want to produce in your oil, and may require some experimentation.

• The simplest and easiest method for small-scale oil extraction is an oil press, though you can also crush the walnuts with a mortar and pestle and gather the oil from the bottom of the bowl. Oil presses can be purchased online and come in a variety of styles.

• Walnut oil has a shelf life of six to 12 months. Store the oil in a sealed glass or plastic container and keep it in a cool, dark place, such as a refrigerator, cellar or pantry. Exposure to air reduces the oil's longevity, so fill the container as full as possible and seal tightly.

• Walnut oil made by crushing walnuts and mixing them with vegetable oil will not produce the delicate flavor for which walnut oil is prized. The flavor of the oil is affected by many steps of the oil-extraction process, including the cleanliness of the nuts, the roasting time and temperature, and storage.

References

• The Epicenter: Walnut Oil
• Practical Answers: Oil Extraction
• National Sustainable Agriculture Information Service: Oilseed Processing for Small-Scale Producers